- Crystal structure, phase transition and conductivity study of two new organic – inorganic hybrids: [(CH2)7(NH3)2]X2, X?=?Cl/Br
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Two hybrids 1,7-heptanediammonium di-halide, [(C7H20N2]X2,X?=?Cl/Br crystallize in monoclinic P21/c, Z?=?4. [(C7H20N2]Cl2: a?=?4.7838 (2)??, b?=?16.9879 (8)??, c?=?13.9476 (8)??, β?=?97.773 (2)°, V?=?1203.58(10)??3, D?=?1.137?g/cm3, λ?=?0.71073??, R?=?0.052 for 1055 reflections with I?>?2σ(I), T?=?298(2)?K. [(C7H20N2]Br2: a?=?4.7952 (10)??, b?=?16.9740 (5)??, c?=?13.9281 (5)??, β?=?97.793 (2)°, V?=?1203.83(6)??3, D?=?1.612?g/cm3, λ?=?0.71073??, R?=?0.03 for 1959 reflections with I?>?2σ(I) T?=?298(2)?K. Asymmetric unit cell of [(C7H20N2]X2,X?=?Cl/Br, each consist of one heptane-1,7-diammonium cation and two halide anions. The organic hydrocarbon layers pack in a stacked herring-bone manner, hydrogen bonded to the halide ions. Lattice potential energy is 1568.59?kJ/mol and 1560.78?kJ/mol, and cation molar volumes are 0.295?nm3 and 0.300?nm3 for chloride and bromide respectively. DTA confirmed chain melting transitions for both hybrids below T?~?340?K. Dielectric and ac conductivity measurements (290??340?K. Cross over from Jonscher's universal dielectric response at low temperatures T??340?K is observed. At high temperatures halide ion hopping in accordance with the jump relaxation model prevails.
- Mostafa, Mohga Farid,El-khiyami, Shimaa Said,Abd-Elal, Seham Kamal
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- Overlap large polaron sensitivity to phase changes in the first alkali earth organic-inorganic hybrid: [(CH2)7(NH3)2]CaCl4
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Crystal structure characterization, lattice potential energy, conductivity relaxation and electric conduction mechanisms of the new alkaline earth metal organic-inorganic hybrid, [(CH2)7(NH3)2] CaCl4 are presented. The new hybrid crystallizes in a triclinic system (S.G. P ̄1) with two molecules per asymmetric unit cell (Z = 2). Crystallographic parameters are: a = 7.029 ?, b = 8.003 ?, c = 14.039 ?, α = 65.43°, β = 69.99°, γ = 61.39°, the calculated volume and density are 620.3 A3 and 1.68 Mgm?3 respectively. Room temperature lattice potential energy is ΔUpot = 1932.34 (kJ/mol.) and enthalpy change ΔH = 453.8 (kJ/mol.). DSC results indicated weak peaks at T7 = 239 ± 1 K, T6 ~ 258.6 ± 0.5 K, a sharp λ-like peak typical of first order T5~ 266.5 ± 0.5 K, a commensurate to incommensurate at T4 = 279 K, an incommensurate to unmodulated at T3 = 283 ± 1 K, and a chain melting transition is noted with minor peak at T2 = 326.5 K and major one at T1 = 329.3 K. Dielectric constant measurements in the temperature range (170–420) K and frequency range 60 Hz- 40 kHz confirmed the DSC transitions. It is characterized by a nearly temperature and frequency independent background of low dielectric constant (ε’) except at the transitions and at T ≥ 344 ± 2 K where frequency dispersion takes place. At high temperatures, calculated conductivity relaxation energy and relaxation time, are ΔE = 0.78 eV and (το) = 7.81614 × 10?14 s respectively. Fit of frequency dependent ac-conductivity to super-linear power law σtot = σdc + A1ωs1+ A2ωs2 shows different conduction mechanisms in the different temperature ranges (phases). Overlap large polaron tunneling (OLPT) of small radius dominates in the temperature range (240–290) K, it is very sensitive to the phase transitions in this temperature range where the polaron radius varies as the phase changes, which is reflected as small variations of the fitting parameters. In phase VIII (T 239 K), phase III (295 T(K) 326.5) and phase II (327 T(K) 339); quantum mechanical tunneling (QMT) is the conduction mechanism. The lower value of the fitting parameters in phase (II) indicates stronger interaction between mobile ions with the lattice than phase (III). At higher temperatures correlated barrier (CBH) hopping prevails. Comparison to other transition metal hybrids of the same organic chain is discussed.
- Mostafa, Mohga F.,Tammam, Ahmed K.
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- Structural characterisation, Hirshfeld surfaces, DSC, periodic DFT modeling, vibrational and optical study of heptylenediammonium pentachlorobismuthate H3N(CH2)7NH3BiCl5
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A perspective hybrid material, NH3(CH2)7NH3BiCl5, was extensively characterized by structural, DSC, spectroscopic (FT-IR, FT-Raman, and UV-fluorescence) and theoretical (periodic DFT/GGA/PBE) methods. The structural features, noncovalent interactions between molecules in the crystal and electronic structure were examined and discussed in relation to the phase transitions, vibrational characteristics and optical properties. The compound crystallizes at 296 ?K in orthorhombic system (Pbcn space group, Z ?= ?8). The Cl?H/H?Cl intermolecular contacts act as the major contributor (77.2%) in the crystal. The compound was stable from the ambient temperature to 503 ?K, and it underwent one-reversible phase transition of second order type near 498 ?K, at heating. Characteristic bands in FT-IR (400-4000 ?cm-1) and FT-Raman (50-3500 ?cm-1) spectra were interpreted based on factor group analysis and calculated vibrational spectrum. The UV-fluorescence excitation at 396 ?nm and the visible region emission at 483 ?nm, which are of Cl(3p) ? Bi(6p) electron transition character, suggest potential applications as UV-filters and blue photoluminescent emmiters.
- Georgieva, I.,Ouasri, A.,Rhandour, A.,Zahariev, Ts
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- Understanding the binding properties of phosphorylated glycoluril-derived molecular tweezers and selective nanomolar binding of natural polyamines in aqueous solution
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A modular synthetic platform for the construction of flexible glycoluril-derived molecular tweezers was developed. The binding properties of four exemplary supramolecular hosts obtained via this approach towards 16 organic amines were investigated by means of 1H NMR titration. In this work, we compare the Ka values obtained this way with those of three structurally related molecular tweezers and provide a computational approach towards an explanation of the observed behavior of those novel hosts. The results showcase that certain structural modifications lead to very potent and selective binders of natural polyamines, with observed binding of spermine below 10 nM. This journal is
- Heilmann, Michael,Knezevic, Melina,Piccini, Giovannimaria,Tiefenbacher, Konrad
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supporting information
p. 3628 - 3633
(2021/05/04)
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- Experimental and Computational Models for Side Chain Discrimination in Peptide–Protein Interactions
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A bis(18-crown-6) Tr?ger's base receptor and 4-substituted hepta-1,7-diyl bisammonium salt ligands have been used as a model system to study the interactions between non-polar side chains of peptides and an aromatic cavity of a protein. NMR titrations and NOESY/ROESY NMR spectroscopy were used to analyze the discrimination of the ligands by the receptor based on the substituent of the ligand, both quantitatively (free binding energies) and qualitatively (conformations). The analysis showed that an all-anti conformation of the heptane chain was preferred for most of the ligands, both free and when bound to the receptor, and that for all of the receptor-ligand complexes, the substituent was located inside or partly inside of the aromatic cavity of the receptor. We estimated the free binding energy of a methyl- and a phenyl group to an aromatic cavity, via CH-π, and combined aromatic CH-π and π-π interactions to be ?1.7 and ?3.3 kJ mol?1, respectively. The experimental results were used to assess the accuracy of different computational methods, including molecular mechanics (MM) and density functional theory (DFT) methods, showing that MM was superior.
- Lidskog, Anna,Dawaigher, Sami,Solano Arribas, Carlos,Ryberg, Anna,Jensen, Jacob,Bergquist, Karl Erik,Sundin, Anders,Norrby, Per-Ola,W?rnmark, Kenneth
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supporting information
p. 10883 - 10897
(2021/07/02)
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- A Modular Phosphorylated Glycoluril-Derived Molecular Tweezer for Potent Binding of Aliphatic Diamines
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A molecular tweezer based on a glycoluril-derived framework bearing four phosphate groups was synthesized and shown to be capable of binding organic amines in aqueous solution. This work reports the Ka values for 30 complexes of this molecular tweezer and amine guests, determined by means of 1H NMR titrations. Both the hydrophobic cavity and the phosphate groups contribute to the binding. Bulkier molecules and molecules bearing negatively charged groups like carboxylates in amino acids bind less tightly due to a steric clash and coulombic repulsion. The narrow cavity and the strong ionic interactions of the phosphate groups with ammonium guests favor binding of aliphatic diamines. These binding properties clearly distinguish this system from structurally related molecular clips and tweezers.
- Heilmann, Michael,Tiefenbacher, Konrad
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supporting information
p. 12900 - 12904
(2019/11/05)
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- Design, synthesis, and solution behaviour of small polyamines as switchable water additives
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The practice of adding salt to water to induce salting out of contaminants or to break emulsions and suspensions is generally avoided industrially because of the expense of the necessary treatment of the salty water afterwards. However, the use of switchable water, an aqueous solvent with switchable ionic strength, allows for reversible generation and elimination of salts in aqueous solution, through the introduction and removal of CO2. In the effort to improve the efficiency of these switchable salts, a physical study modeling their reactivity and solution behaviour has been performed, resulting in a set of design principles for future switchable water additives. The resulting polyamines synthesized using this template show the highest efficiency recorded for a switchable water additive. The Royal Society of Chemistry 2012.
- Mercer, Sean M.,Robert, Tobias,Dixon, Daniel V.,Chen, Chien-Shun,Ghoshouni, Zahra,Harjani, Jitendra R.,Jahangiri, Soran,Peslherbe, Gilles H.,Jessop, Philip G.
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supporting information; experimental part
p. 832 - 839
(2012/04/23)
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